1. Technical Field
The present invention relates to a technique for calculating the amount of toner which is consumed as an image is formed by an image forming apparatus.
2. Related Art
An image forming apparatus of the electrophotographic type, such as a printer, a copier machine and a facsimile machine, which forms an image using toner must know, for the convenience of maintenance including replenishment of toner, a toner consumption amount or a remaining toner amount. In response to this, techniques for accurately calculating the amount of toner which is consumed as an image is formed have been proposed. For instance, according to the toner consumption amount detection method described in JP-A-2002-162800, the tone values of print dots expressed in multiple tones are summed up for one page, thus obtained integration value is multiplied by a predetermined coefficient and an offset amount which corresponds to the amount of toner which is consumed without contributing to image formation is added to the resultant value, whereby a toner consumption amount is calculated.
In general, an image forming apparatus of this type performs data processing of input image data to thereby obtain a predetermined image quality. Such data processing is executed for the purpose of controlling the density of an image eventually formed on a recording medium to a predetermined density. Meanwhile, it is known that there is a non-linear relativity between the amount of toner constituting an image and the density of the image. Due to this, a relationship between image data and the amount of toner constituting an image corresponding to the image data as well may be non-linear in some instances.
As for such instances where the conventional techniques above are used, since the tone value given to each print dot is an adjusted value so that a predetermined density will be obtained on a recording medium, the tone values of the print dots and a toner consumption amount are not always proportional considering the non-linearity described above. The conventional techniques above however have not taken this feature into consideration sufficiently, leaving a room for improvement with respect to the accuracy of calculating the toner consumption amount.